Szilvalekvár

Step 1: Put the stoned 6 ⅝ lb very ripe prune plums (Hungarian or Italian) in a large, heavy, wide pan with the ½ cup water (and the 1 cinnamon stick and 3 cloves if using). Cover and cook over a medium heat for 20 minutes, stirring now and then, until the plums collapse into juice.

Step 2: Remove the spices and blend the fruit smooth with a stick blender, or press it through a coarse sieve to remove the skins.

Step 3: Cook uncovered over a medium-low heat for about 1 hour, stirring every 10 minutes and scraping the base, until it has reduced by about a third.

Step 4: Heat the oven to 300°F (275°F fan) and scrape the purée into a large roasting tin. Bake for 2½–3 hours, stirring every 30 minutes, until very thick and dark brown; a spoon drawn across the bottom should leave a clear path that stays open.

Step 5: Wash the jars and lids in hot soapy water, rinse, then sterilise: jars upright in a 275°F oven for 15 minutes, lids in boiling water for 5 minutes. Keep them hot until you fill them.

Step 6: Fill the hot jars with the hot plum butter to 1 cm from the top, tapping to remove air pockets. Wipe the rims and seal tightly.

Step 7: Process in a simmering water bath, water 2 cm over the lids, for 10 minutes, then cool and check that the lids have sealed. Store as described above and refrigerate once opened.